1 dead, more than 40 sick as legionnaires' outbreak spreads in southeast London

One person is dead and at more than 40 people sick after a legionnaires' outbreak in London, Middlesex London Health Unit officials say.

The health unit has declared an outbreak and said the cases were reported within the last week. Most of the cases live and/or work in a six kilometre radius of one another in the southeast side of the city, officials say.

"The health unit is working in close partnership with Public Health Ontario and the Public Health Ontario Laboratories to investigate and identify the source of the outbreak," health unit officials wrote in a statement on Tuesday. "Environmental sampling of potential sources of legionella is ongoing. Since legionella can be found in many types of cooling systems, the investigation may take time."

Legionnaires' disease is a serious respiratory illness caused by legionella bacteria, naturally found in water sources such as hot tubs, cooling towers, hot water tanks, large plumbing systems or parts of air-conditioning systems.

If the bacteria are then aerosolized or misted into the air (via wind or fans), people may inhale the bacteria and become unwell.

Most people exposed to legionella do not become ill, though some may experience a milder illness called Pontiac fever, which resolves itself.

Individuals who are older, have lung problems or are immunocompromised are at greater risk for serious infection. Legionella is not transmitted from person-to-person.

Anyone who develops symptoms including fever, cough and shortness of breath are encouraged to seek medical attention. All business owners and property managers should ensure all cooling equipment is regularly maintained and sanitized as per the manufacturer's instructions.

Although face masks can decrease the risk of infection, the health unit is not recommending regular community-wide face mask use specifically for the prevention of legionnaire's disease, as the public risk is low.

This is the second outbreak legionnaires' disease to occur in London in two years. Last year, an outbreak localized in the city's east end led to two deaths and 30 total reported infections.

"At this time, it is not known whether it is the same location as the legionnella outbreak from last year," the health unit said. "However, this is being considered as part of the ongoing investigation."

More to come